#define _CRT_SECURE_NO_WARNINGS 1

#include<stdio.h>
int Sum(int a)
{
	int sum = 0;
	for (int i = 1; i <= a; i++)
	{
		sum += i;
	}
	return sum;
}
int Squ(int b)
{
	int sum = 0;
	for (int i = 1; i <= b; i++)
	{
		sum += (i*i);
	}
	return sum;
}
double Rec(int c)
{
	double sum = 0;
	for (int i = 1; i <= c; i++)
	{
		sum += (1.0 / i);
	}
	return sum;
}

int main()
{
	int a, b, c;
	scanf("%d%d%d", &a, &b, &c);
	double sum = 0;
	sum = Sum(a) + Squ(b) + Rec(c);
	printf("%.2lf", sum);
	return 0;
}